The present invention relates to an improved mounting and fastening device for modular panels, boards or cards which, in turn, mount circuits such as printed circuits, within a panel rack or cage utilized in connection with electronic equipment or the like.
The present invention is an improvement in the "COMPOSITE PRINTED CIRCUIT CARD GUIDE AND HOLDING DEVICE" disclosed in U.S. Pat. No. 3,950,057 which issued on Apr. 13, 1976 to Anthony D. Calabro, and which is assigned to the assignee of the subject application, as well as an improvement to the invention disclosed in U.S. Pat. No. 4,096,547 which issued to Anthony D. Calabro on Jun. 20, 1978, and is entitled "HEAT TRANSFER MOUNTING DEVICE FOR METALLIC PRINTED CIRCUIT BOARDS", which patent is also assigned to the assignee of the subject application. The disclosures of U.S. Pat. Nos. 3,231,785, 3,950,057 and 4,096,547 are incorporated herein by reference.
In connection with the mounting of printed circuit boards and the like, reference is made to U.S. Pat. No. 3,231,785 which issued on Jan. 25, 1966 and is entitled "CIRCUIT BOARD MOUNTING DEVICE", also assigned to the assignee of the subject invention, which discloses the basic concept of an integral holding device which includes unitary spring fingers for securing the above-mentioned panels, such as printed circuit boards, within a rack or cage mounting. For applications where the printed circuit board or panel is on the order of seven or eight inches, the unitary circuit board mounting device disclosed in said U.S. Pat. No. 3,231,785 is excellent for maintaining a printed circuit board in place, even in the presence of shock and vibration. The patented printed circuit board mounting device of U.S. Pat. No. 3,231,785 is of unitary construction, preferably of a plastic material which, over a relatively short length of approximately eight inches, is fairly rigid in order to securely hold the printed circuit panel. However, with advanced technology, it has been found that there are requirements for mounting large size printed circuit boards, on the order of two to three feet, in a stable condition, and in a manner so as to provide support for the board for spanning large open spaces. In addition, considering the number of components mounted on the board, there is a great need for providing means in the form of heat conducting surfaces for achieving good heat transfer from the printed circuit board to the surrounding structure or atmosphere. Still further, in certain applications it is desirable that the circuit board mounting device should also provide electrical grounding for the printed circuit board. Another feature which is often desired is to provide spacer or gage means for assisting the spring finger dampening means from overstressing the fingers due to vibrations of the printed circuit board brought about by either mechanical vibrations in the chassis of the electronic system, or by the vibrations created in the printed circuit board when electrical power is applied thereto.
U.S. Pat. No. 3,950,057 entitled "COMPOSITE PRINTED CIRCUIT CARD GUIDE AND HOLDING DEVICE" which issued on Apr. 13, 1976, and is assigned to the assignee of the subject application, achieves the objectives set forth above. U.S. Pat. No. 3,950,057 discloses a composite printed circuit card guide and holding device comprising a U-shaped elongated member made of a rigid material, and including two upstanding arm members having inwardly directed flanges which are spaced a sufficient distance to enable the passage therethrough of the edge of a printed circuit card. Printed circuit card engaging means are slidably received within the U-shaped member, which printed circuit card engaging means includes a plurality of opposed, cantilevered flexible spring fingers extending into the region where the printed circuit card is mounted, thereby resiliently engaging and holding the printed circuit card. With the U-shaped elongated member being made of a rigid material, such as an extruded metallic material, such as aluminum, and with the printed circuit card engaging means formed of a flexible plastic material, there is achieved a composite printed circuit card guide and holding device which is rigid for maintaining and holding a large printed circuit board that spans over large open spaces; which inherently includes good heat conduction characteristics for transferring heat from the printed circuit board to the surroundings; and which device is made of good electrically conducting material so as to provide the capability of grounding the printed circuit board, when required.
A further improvement in the composite printed circuit card guide and holding device is disclosed in U.S. Pat. No. 4,096,547 which issued on Jun. 30, 1978 to Anthony D. Calabro and is entitled "HEAT TRANSFER MOUNTING DEVICE FOR METALLIC PRINTED CIRCUIT BOARDS", and which is assigned to the assignee of the subject invention. The printed circuit board guide and holding device of U.S. Pat. No. 4,096,547 is particularly adapted for use with metallic printed circuit boards, and has improved heat transfer capabilities comprising an elongated heat transfer support member which is adapted to receive the printed circuit board engaging means. The heat transfer support member is of generally U-shaped cross section and is made of metallic material, with the upstanding arms including spaced flanges to enable the passage therethrough of the edge of the printed circuit board. One of said flanges includes a depending heat conductive element that is adapted to directly engage and be in intimate contact with the metallic printed circuit board to facilitate the conductive transfer of heat from the board to the support member.
Notwithstanding the efficient operation of the composite printed circuit guides described in U.S. Pat. Nos. 3,950,057 and 4,096,547, it has been found desirable to provide further improvements to a composite circuit board guide in several respects. In one aspect, it has been found that, occasionally, because of the frictional interengagement between the U-shaped elongated member and the printed circuit card engaging means, when a printed circuit board is removed from a cage or the like, the frictional force holding the card engaging means in the U-shaped member is less than the pulling force applied to the printed circuit card, and as a result the printed circuit card engaging means are inadvertently removed from the U-shaped elongated member, along with the printed circuit board. In order to overcome this shortcoming, the subject invention provides a new and unique interconnection between the printed circuit card engaging means and the U-shaped elongated member, thereby obviating inadvertent removal of the circuit card engaging means from the U-shaped elongated member.
In a second aspect, in the prior art system as disclosed in U.S. Pat. No. 3,950,057, in order to attach the composite printed circuit card guide and holding device to a cage or the like, a separate, discrete clip is provided for interconnecting the U-shaped elongated member to the cage structure. In order to provide a simpler, more efficient interconnection between the composite printed circuit card device and the cage, the U-shaped elongated member of the subject invention includes unique end structures, whereby opposed distal ends of the U-shaped elongated member include unitary means for attaching the composite holding device to the cage, without the use of a separate discrete member, thereby aiding in more rapid assembly and efficient operation of the composite printed circuit card guide and holding device.
In a third aspect, in the prior art systems as disclosed in U.S. Pat. Nos. 3,950,057 and 4,096,547, the opposite ends of the base of the U-shaped printed circuit card engaging means are disposed over the base of the U-shaped elongated member thereby forming steps or obstructions to the smooth entry of a printed circuit board being slidably inserted into the composite board guide. The subject invention overcomes this problem since the opposite ends of the U-shaped printed circuit card engaging means are received within slots in the elongated member thereby ensuring an unobstructed smooth entry of the printed circuit board into the composite guide and holding device of the subject invention.
Accordingly, it is the object of the subject invention to provide a new and improved composite printed circuit card guide and holding device wherein the printed circuit card engaging means is interengaged and connected to the elongated U-shaped member in order to prevent disengagement of the engaging means from the elongated member, and to ensure smooth entry of a printed circuit board into the subject guide and holding device.
It is a further object of the subject invention to provide a new and improved U-shaped elongated member that includes tapered distal ends, with an aperture being provided in each distal end to accommodate attachment of the U-shaped elongated member to the printed circuit board cage or other assembly without the requirement of a discrete clip, as in the prior art systems.